Nuclear reactor ultrasonic inspection devices have long been available for scanning welds when a reactor is shut down for refuelling and its open reactor vessel is submerged in a water pool. Such devices typically include a spider assembly having legs spanning the reactor vessel flange at its open upper end, a telescopic vertical column mounted in the hub of the spider coaxial with the vessel, and a telescopic horizontal boom at the lower end of the column carrying the scanner. U.S. Pat. No. 3,780,571 is typical of the disclosures of such devices.
It is characteristic of prior art inspection apparatus that they involve complicated telescopic and rotational drives often with pulley and cable systems, all of relatively high cost and substantial weight. It is the principal purpose of the present invention to provide a method and apparatus for displacing a reactor weld scanner into and out of position by a system which is inexpensive and which can be assembled at the site with lightweight individual parts transportable by one man.